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Can a helicopter have a fully mechanic "elevator"?
After a research, I've seen prototypes of planes with elevators. What if it could be used as part of the "Air Ambulance" technology on helicopters? Because helicopters have to land first to pick up patients, would it be better to use an "elevator" to lift them into the helicopter when it is hovering?
If this have been made before, can you point to a prototype?
And if not, why it haven't been made? Is it non-doable in terms of physics and engineering?

I'm not a pilot, but I'd say that in sims a stable hover at set altitude vs landing are tasks of comparable timeframe

I have issues understanding the question. what would be a timeless transportation? teleport? also, in avioation the term "elevator" has a specific meaning, are you referring to a lift/winch system?

Extinction as in 'no longer exist' as in dinosaur extinction. Or just my bad english?

@vasin1987: I believe t0r meant 'extent'.

Don't understand your question. "Planes with elevators"...which planes? links to the information you are referring to please.

Using a building elevator would cut the payload of the helicopter in an unacceptable way. Also, none of the safety features of a building elevator could be implemented, and in the end you will have a cage lowered on a rope. Which is quite similar to existing winch systems.

Elevator components (source)
In addition to the motor and the pulleys, a building elevator has a car which runs along guide rails, and a counterweight to compensate for the heavy car. Adding all this to a helicopter would require a much bigger machine just for carrying the elevator components around. Note that using guide rails would dictate a specific hover height - no helicopter pilot would agree to have his options restricted that severely.
Lowering anything in the downwash of a helicopter rotor will cause it to swing and rotate, and putting the occupants into a cage will cut their ability to stabilize themselves or the cage. Once the cage is raised all the way up, it needs to be oriented correctly for easy egress. A rescuer on a rope can easily stabilize himself by grabbing handles on the outside of the helicopter. Sitting in a cage, he can only watch helplessly when the cage arrives in the wrong orientation.
There are many scenarios where rescue helicopters cannot land, like over water or over a forest. In those situations a winch is used to hoist one rescuer down to the ground, where he/she can pick up the injured and secure them to their harness. Both of them are then raised up and taken on board. Only when the patient must not move (think fractured leg), a platform is used to secure the patient. See below for a simulator installation, and note that still a rescuer is needed to stabilize the platform.

Helicopter rescue hoist trainer (source)
If the ground allows, landing the helicopter is simpler, makes much less noise and makes it immune to changing winds. Also, lowering the rescuer first and landing the helicopter will take a similar amount of time, so no substantial time savings can be expected.

AgustaWestland AW139 helicopter on SAR exercise (source)

he says in the comments that he is specifically not referring to winch systems.

@Federico: Thanks for pointing this out. It is always fun when people only make up their mind what to actually ask when the answer is being typed.


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Currency retraining
I am a private pilot who has not flown in 30+ years, but want to start again.  I'm a little concerned about how airspace and avionics may have changed.  Will be starting with CFI next week.  Can anyone give me an overview of what I might encounter? Cessna 172, SEL, Private no IFR.

Welcome to the Aviation.SE.The first document on this FAA list (advanced avionics)  and the Aeronautical Information Manual a few rows after may provide you with a general view, I just fear it could be a lot of information at once.

Related: http://aviation.stackexchange.com/questions/67/how-do-i-renew-revalidate-my-lapsed-easa-ppl

To regain your currency there are a few things you need to do legally.
Medical: The first thing you will need to do is get your medical cert back, to fly with a CFI this is not mandatory since they are technically acting as pilot in command but you will need it before you can act as pilot in command.
Bi-Annual: You will be required to do your bi-annual flight review which legally is one hour of ground instruction and one hour of flight time instruction to become current.
Landings: Although you will most likely knock this out during your bi-annual, before you carry passengers you will need to do 3 TO/LD for day currency and 3 full stop night TO/LD for night currency. Since you may need a few hours of instruction to feel comfortable I would set up at least 1 night hour to get these landings in.
In terms of what has changed in the last 30 years...
The 172 is still a 172 and the yoke is still in the same place. In terms of what you will encounter in the cockpit this will vary from plane to plane. Lots of trainers are old planes and or set up as they were more or less 30 years ago. The biggest difference you will find is the role and inclusion of GPS. While its not required (yet...) a lot of planes have the common Garmin 430 or 530 units and some planes out there may even have a full G1000 setup. Much of this depends where you rent from. You will still be able to get all your paper charts as you once could but many people are moving into the tablet/e-flight bag revolution which can really revolutionize how you fly. You may want to check out ForeFlight and the like to see what they have to offer.
The FAA offers lots of free handbooks that can be found here. Of particular interest might be Pilot's Handbook of Aeronautical Knowledge, Aeronautical Information Manual, and this overview on airspaces.

It has been said, on average, to expect at least one hour dual instruction for each year out of currency.  In your case, at least 30 hours.

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Flaming plane-like object in the night sky
In this video on X from February there is a flaming apparition in the sky over downtown Charlotte, North Carolina that looks like the Spruce Goose on fire. It does not look fake to me, but I cannot rule out that possibility.
Here is a still image from an article in the Mirror which was actually, like me, wondering what it was (they really should ask on aviation SE!):

It does not look like a regularly operating plane. But it is too low for space debris and actually changes course after a few seconds.
I tried to find information about a burning plane but didn't see any; partly because burning plane hits currently are heavily dominated by the Tokyo incident.
Therefore the question: What the heck are we looking at?

It is the pyrotechnic Bandit Fly Team flying over the Carolina Hurricanes Stadium in North Carolina on 18 February 2023.

There are a large number of videos online of the event, including one from the Bandits themselves, which also shows the rather spectacular view from inside the cockpit.
However, there are an even larger number of videos speculating on alien origins, which even made the press (UK).

Good find even though my original question was terribly vague. Through the link to the X video in the Mirror article you link to I was able to provide more information which I included in the question.

If this is Charlotte, in all likelihood, it is the Carolina Panthers NFL stadium. The Carolina Hurricanes are an NHL team and are based in an enclosed arena in Raleigh, North Carolina.

You got some of the details wrong here. Please see my answer. I am willing to delete my answer if you update yours.

@MJ713 Why don't you just submit an edit to this answer, fixing the incorrect information?

@TomWalker: The NHL does a few open-air stadium games each year.  In 2023 they did one in Raleigh. The stadium in question was Carter-Finley Stadium, home of the North Carolina State football team.

@TooTea I felt it would be rude. Fixing typos is one thing, but in my experience people get touchy if you change their answer on a fundamental level.

This was indeed a pyrotechnic display by the Bandit Flight Team, as Party Ark's answer states, and it was a flyover for a hockey game. But that answer gets the city, date, and hockey team wrong.
Per the Charlotte Observer's article about your linked video, the Bandits did this flyover for the Queen City Outdoor Classic in Charlotte, North Carolina on January 13th, 2024. This was an AFL (i.e. minor-league) hockey match between the Charlotte Checkers and the Rochester Americans. The ice rink was, as the name suggests, outdoors.

Oh, interesting. The article is pretty convincing, in particular because it shows exactly the video I was looking at. I'll let your answer sit for a while and see whether Party reacts, as per your suggestion.

Thanks for the clarification - however, the Bandits' own video I linked to was posted in November 2023, so this clearly wasn't the only occasion this might have been seen. I imagine when they do this night flying it all looks very similar anyway.

Since the question is about a specific video, I think it can be stated pretty conclusively that the first answer is correct that it was a Bandit Flight Team flyover, with the second answer giving the correct date and location.
The YouTube video originally linked to was posted on January 23rd, 2024. The posting on X that was subsequently linked to was posted on January 21st, 2024 although it is not stated when the video was taken.
As mentioned the Bandit Flight Team had a scheduled flyover of a hockey game to be held at Truist Field in downtown Charlotte, North Carolina on January 13th, 2024 at 7:00 pm EST.
FlightRadar24 on that day shows one of the Bandit Flight Team aircraft, a Van's Aircraft RV-8A registration N592MB, making a flyover of Truist Field on January 13th, 2024 at 7:17 pm EST (12:17 UTC January 14th) at an altitude of 1,925 feet.

With the flight path through downtown generally following 3rd street.

This seems to be the only aircraft in the formation that was broadcasting ADS-B data at the time.
Using landmarks in the video, it can be confirmed that the vehicle taking the video was travelling northbound towards downtown on 4th street. The video is taken as the car travels about 1/10th of a mile, the video concludes as the vehicle reaches North Kings Drive.

This view is consistent with the path of the aircraft seen in the video.
The vehicle path is shown in red in the map below.

In this screenshot from a video on the Bandit Flight Team website, N592MB is the airplane at the bottom of the photo.

Good job. I could have thought of that.

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How do airports in hot climates handle extremely high temperatures?
In June 2017 dozens of flights were cancelled in Phoenix, Arizona because of temperatures exceeding 120 degrees Fahrenheit/48.9 degrees Celsius.1,2
Hot air at a given air pressure is less dense, generating less lift at a given speed. At least some commercial jets were not rated to fly in air that thin.
While the temperatures that summer were fairly extreme Phoenix is surely not the hottest place one earth, or at least not alone in this range. For example Kuwait City or the Iranian city of Ahvaz3 come to mind.
How do other hot places handle extreme heat? Do they also suspend operation or do they impose specific requirements like lower maximum loads, or do they have special adaptations for the thinner air like long runways, allowing higher speeds at take-off and landing?

1 https://airlinegeeks.com/2017/06/22/multiple-flights-cancelled-due-to-heat-in-phoenix/
2 https://www.sciencedirect.com/science/article/pii/S2212012218300753
3 I found Ahvaz googling for hot places; I admit that I have never heard of it before even though it has more than a million inhabitants and an international airport, AWZ.

They wait until the weather cools.

Planing longer runways, and not obstacles nearby.

FYI, it generally isn't the airport making the call on operations like this, it is the aircraft owner/operators.

@ymb1 Thanks for the pointers. The chart in your answer there indicates that longer runways can make up for higher temperatures. But then there appears to be a hard climb limit as well.

Transport aircraft are certificated to a maximum operating temperature for departure that is related to International Standard Atmosphere (ISA), typically 35 deg C above ISA (there may be airplanes certified to ISA +40), ISA being 15C at sea level and dropping from there at the standard adiabatic lapse rate .
ISA temperature at Phoenix airport at 1135 ft ASL is about 13 deg C, so the max temperature you can operate at is 48C, if your plane is certified to ISA +35 (if your plane was certified to ISA +40, you'd be good to 53C).  This is based on the airport temperature reported on ATIS, not temperature measured at the aircraft.
At 48.9 C in the case you mentioned, you are above your maximum certified temperature for takeoff, so you are stuck until it cools off, and you'll simply have to wait for the temperature to drop a degree later in the day.  This applies anywhere in the world based on the ISA temperature for the airport. So for example at a Middle Eastern airport at sea level, where ISA is 15C, you'd be good up to 50 deg C, and if it's above that temperature, you wait for it to cool off.


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Which airplane is visually crossing the path of the descending Dragon spacecraft on Sept. 18, 2021?
In the recording of the SpaceX live-stream covering the return of the Inspiration4 crew in the Dragon spacecraft one can see an aircraft visually cross path with the capsule at 22:59:58. While the encounter is stunning to see, the proximity is surely just apparent, owed to the viewing angle and extreme focal length of the lens. I asked a question over on space exploration but it occurred to me that many aspects are actually aviation questions. Here are my questions regarding the aviation side of the incidence.
The video is apparently taken from another aircraft. The GPS data visible in the upper left corner indicates an altitude of "20.846 "20,846" (?), I suppose 20.846 km 20,846 feet, above mean sea level.
At closer inspection, the crossing airplane seems to me at an angle of maybe 15 or 20 degrees above or below the horizontal plane (the vertical stabilizer seems visible and the wings seem to appear at a flat angle).
I have the following questions:

Which airplane was that? In particular, was it a another flight related to the landing, operated by SpaceX?
At what altitude was the crossing airplane flying at that time?
From what I have read, the landing zone is in international waters outside the jurisdiction of the FAA; therefore, no Temporary Flight Restriction can be issued. Instead, a general Notice to Airmen is issued whose character, I understand, is advisory. (This resembles the situation on sea where the coast guard merely "discourages" vessels to enter the exclusion zone.) Did such a Notice to Airmen exist? If the airplane was not SpaceX's, was it violating/ignoring that notice?

The following image is a frame from the video. The bright dot in the middle is the capsule. I'm not sure what the direction of the shot is, whether it is pointing upwards or downwards, and at what angle. Knowing the altitude of the other plane would give us an idea.

20.846km is over 68,000 feet, that's unusually high for most aircraft.

You've already asked this on Space.SE, please do not cross-post.

@GdD While the questions are (closely) related I hope they differ enough: Aviation is more suited to ask identification and regulation questions while space exploration is perhaps better for asking about safety issues related to the re-entry. I should edit the space exploration question though to make the focus clearer, now that I turfed the aviation part here.

@GdD I made the relation explicit to avoid confusion.

@Peter-ReinstateMonica I deleted my answer. I did more research about where this footage is recorded from. Unfortunately I don't know much about SpaceX and haven't been able to find out for sure. However, everything I saw points at the WB-57. If that's true, then it cannot have been the aircraft flying in front of the camera.

Unless there were two of them, @Bianfable! ;)

@FreeMan FR24 only shows one. The other two did not fly that day.

About how the recording is done using AIRS on the WB-57 (apparently NASA926 flight number), in case that can help. AIRS is able to record the heat wake at a distance of 150 km. Some explanations on the observation in the video of a previous reentry at the end of the page.

@Bianfable I posted an answer which seems to agree with the known facts. There is a FedEx jet potentially crossing the line of sight at the right moment. The WB-57 was a good bit of information, but as you suspected later, it did the video.

As Bianfable already posted in their deleted answer, the only aircraft in the NOTAM zone at this point in time is one of NASA's WB-57s, the N926NA. According to an article on spaceflightnow.com, NASA deployed the surveillance aircraft in exchange for permission to "inspect the [para]chutes before and after the flight" (thanks to mins for the detail). The WB-57 filmed the reentry with one of its specialized equipment, the Airborne Imaging and Recording System (AIRS). The system was originally designed to inspect space shuttles during the ascent phase in order to detect potential damage of the kind that led to the loss of Columbia. It can take infrared videos at extreme range.
The N926NA is flying at 20,000 feet. The camera is looking roughly southwest in the direction of the incoming capsule. The only information about that is from the same video at 20:14.1 The assumed splashdown location and orbit implies that during the video the capsule is crossing Florida at a rapidly decreasing altitude between 80km and around 30km; the thresholds are the beginning and the end of comms blackout due to the ionized hot atmosphere surrounding the entering capsule. The capsule is seen from below, as are jets at the cruising altitude of 30,000 feet.
After looking at the details I think the only aircraft crossing the visual axis towards the incoming Dragon spacecraft is FedEx FDX251, at this point flying at 38,000 feet, according to flightradar24.

The image is a screenshot of flightradar24 with the location of the two aircraft involved at the approximate time of the pass. The red arrow is a pretty wild guess of the Dragon trajectory with an estimated splashdown location of 80.3W 28.8N from here, the only site I could find that provides splashdown coordinates at all. Note that the precision of 0.1 degree corresponds roughly to a distance of 10 km. In an admittedly circular reasoning I adjusted the Dragon trajectory so that it would result in the observed scenario of the three objects being in line, and the Dragon about 4 or 5 times as far as the FedEx plane, dictated by the three objects' altitudes. The green dotted line is my guess at a line of sight from N926NA. Of course all data is inexact (aircraft locations) or unknown (Dragon positions), but it is safe to say that I can construct a scenario which doesn't contradict what we know.
The direction of the crossing aircraft in the video, coming from the right into our south-west facing visual axis, matches the south-east bearing of the FedEx plane. As can be seen, FDX251 is at this point roughly 40 km away from the camera, but the capsule is much farther: At an altitude of 30km, or 100,000 feet, it would have 80,000 feet altitude difference to the NASA plane; that is four or five times as much as the 18,000 feet difference between the NASA plane and the FedEx plane. If they are on the same axis, the capsule is four or five times farther away, in my guessed scenario where the line of sight intersects with the capsule's path.
I find it noteworthy that a few minutes earlier the FedEx jet was probably in a location, including the altitude, that is very close to where Dragon will be just a few minutes later.

1 The trajectory in the video shows an approach across Cuba, not Florida, but I think the close proximity to the shore (if the estimated landing coordinates are correct) means it overflew Florida. But all of this is a conjecture based on incomplete and unverified information. I'll ask over at space exploration whether Dragon indeed flew over Florida.

"SpaceX must have rented it to film the reentry". From SpaceFlightNow SpaceX had a contract with Nasa: "NASA will also deploy a WB-57 surveillance aircraft to collect imagery of the Crew Dragon’s re-entry, parachute deployment, and splashdown at the end of the Inspiration4 mission, in exchange for NASA access to inspect the chutes before and after the flight".

@mins Ah, interesting detail!

@mins Thanks. The linked Youtube video has a UTC time counter in the images from the AIRS, so we know the time of the pass exactly.


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How to calculate normal takeoff ground roll when the POH only has Short Field Takeoff tables?
The Cessna 172S POH only has Short Field Takeoff Distance tables.  How do pilots determine ground roll for a normal takeoff on a long field with hard surface?
The examples in the POH only deal with short field takeoff.  Similar thing with chapter 10 in the Pilot's Handbook of Aeronautical Knowledge.  It's either short field takeoff or referring to charts that don't exist in the Cessna 172S POH.
Do pilots look up the short field ground roll, apply the adjustment factor for headwind and apply another adjustment factor?
The POH says, on page 5-4 "...keeping in mind that the distances shown are based on the short field takeoff technique.  Conservative distances can be established by reading the chart at the next higher value for weight, altitude and temperature."
Does that mean to use the chart, but use the row for the next highest PA and the column for the next next highest temp when determining normal takeoff ground roll?
I've searched this forum and haven't found anything applicable.

In the C172S POH I have, it's on p. ii (Performance - Specifications): 960ft ground roll and 1630ft total over a 50ft obstacle. The note on p. iii says:

The above performance figures are based on airplane weights at 2550
  pounds, standard atmospheric conditions, level, hard-surfaced dry
  runways and no wind. They are calculated values derived from flight
  tests conducted by Cessna Aircraft Company under carefully documented
  conditions and will vary with individual airplanes and numerous
  factors affecting flight performance.

In other words, it's a useful number to know but you're unlikely to get exactly that performance unless you're a Cessna test pilot in a brand new aircraft. If you own the aircraft (or rent it often) you might want to spend some time actually measuring takeoff distances yourself, to see what performance you're really getting.

I wonder how one can measure takeoff distance themselves. Without suitable equipment and proper training, one is unlikely to conduct measurements to obtain accurate and usable results.

Ok I found that page.  So that would give a reasonable safety margin given that the aircraft fully fueled and with 1 occupant will be lighter and take off faster, not considering actual PA and wind factors?

@kevin If you take off on a runway that has a precision approach, there are white bands spaced every 500'. The centerline stripes are usually about 100' apart, so you can use them for guidance as well. Try some takeoffs with various winds and loads and you’ll know what you can expect with your airplane and your skills. Check out the AIM 2-3-3. Runway Markings for details.

@kevin There are a few options, from just looking out the window to GPS tracking. You only have to be accurate enough for whatever your own scenarios are.

@Kinmount I don't really know what you mean about a safety margin. POH values are typically best case, because they're gathered using an expert pilot. But in this specific case, the figure is given with no wind, so if you have a headwind on takeoff then you should need much less distance. As the POH says, there are a lot of variables involved.

@Pondlife what you said is what I meant.

I'm actually surprised the short field takeoff only improves takeoff distance by around 3.5% compared to a normal takeoff in the same conditions.

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Taxiing with one engine: Is engine #1 always used or do they switch?
I recently travelled with an A320 and an A321 from FRA (Frankfurt) to TXL (Berlin) and back again. On this and on previous flights I already noticed a whining sound, much louder than other sounds, while we were still at the gate or soon after leaving the gate and starting taxiing. I cannot remember exactly. My research showed that this was the PTU's sound (aka “barking dog”), typical for an A320 and its sisters.
One of my references was this post. The author said:

[The PTU can be heard]
      At the gate, especially if we taxi in on one engine.
      During the taxi, the left engine is running and pressurizing
      the green system.

This led me to this question:
When taxiing with one only engine, do pilots always use the left-most one (#1)?
Or do they randomly choose one of the two (or four)? If they always use the port/port outer engine, doesn't it wear out sooner? Or are the engines swapped at regular intervals (like car tyres  are swapped from front to rear)?

OpSpecs may prohibit the use of one engine on taxi.  I worked for an operator who required two engine taxi to reduce (waht they thought was) excessive and needless sideloading of the nosewheel.  This operator has also killed a number of pilots and has a depressingly bad accident/incident rate, so take their behavior with a grain of salt.

Not an answer, but notice that wearing both engines equally might not be desirable. You don't want them to approach their end of life at the same rate, to minimize the chance of a double failure.

Airbus aircraft have 3 hydraulic systems (Green, Blue, Yellow). Green is pressurized by left engine, Yellow by right engine, and each one can be pressurized by the other using the PTU. In addition the Yellow circuit has an electric pump.
The Blue circuit is a backup pressurized on demand by several means (electric pump and RAT).
Each circuit powers different aircraft components:

Source: A320 FCOM
The choice of which engine(s) to use is based on the need to have pressure:

For brakes
For nose wheel steering system.

Normal brakes and nose wheel steering are pressurized by the Green system. The brake accumulator must be pressurized, this can be done by running the an electric pump without starting an engine..
Engines are numbered 1 for left, 2 for right on twin-engined aircraft and from left to right (1/2 and then 3/4) for four-engined aircraft.
From this document:
Which Engine to Use?

A320 Family: ENG 1
  A330: ENG 1
  A340: Outer engines (ENG 1 + 4)

Why?
A320 Family:

ENG 1 pressurizes GREEN HYD (NWS + NORM BRAKE)
YELLOW HYD pressurized via ELEC PUMP
PTU is not needed

A330:

ENG 1 pressurizes GREEN + BLUE HYD
HYD BLUE ensures ACCU PRESS
ELEC PUMP are not needed

A340 (outer engines when possible -- exception would be a narrow taxiway and FOD risk):

ENG 1 + 4 pressurize GREEN HYD (NWS + NORM BRAKE)
Check ACCU PRESS normal before ENG start
ELEC PUMP are not needed

Great answer. Especially the Which and Why sections. I'm still curious about the wear of ENG 1 compared to ENG 2 when ENG 1 is always favoured but I'll post another question on that. Perhaps. ;-)

If ENG 2 would be used (on the A320), it would pressurize the Yellow system, but not the Green one. So normal breaks and steering system would not be active unless the PTU was used. To prevent the PTU to be active, this is done with ENG 1 (and only the electric pump of the Yellow circuit if the brake accumulator is not pressurized enough -- no PTU, no right engine).

So the intention is to not use the PTU deliberately. Understood. NWS either works with ENG1 or ENG2+PTU. Given that, using ENG1 is the simpler choice.

@PerlDuck: Also the PTU wont' work when the parking brake is set (though I'm not sure for all A320 family aircraft).

Just to be sure that I understood the diagram: when ENG1 (or the green system) fails in-flight the PTU pops in to allow for lowering the gear (beyond other things), right?

@PerlDuck: Right, as soon as there is a difference of pressure between Green and Yellow of more than 500 PSI. Here is the full logic from the FCOM.

@PerlDuck, the PTU is an emergency-only thing. It tends to heat up rather quickly, so you don't want to use it during taxi so it's not already hot in case you needed it due to engine problem during take-off.

I can't say if pilots always use the same one engine for taxi in or out. However, if they do, that engine probably lasts longer and the other one wears out sooner. The reason is that engine life is highly dependent on low cycle fatigue due to thermal cycles (i.e. cold then hot then cold). If you start a cold engine and immediately go to takeoff, the thermal transients inside are more severe than if you let it warm up at idle for 10 minutes. Same on landing. Shutting the engine down immediately after landing is more severe than cooling off at idle for a few minutes.

There are aircraft limitations for warm and cold startup a and cool down time limits to prevent wear like this.

This is not true for commercial jet engines.  There are limits to how long the engines must run for after start before take-off depending on the engine types, SOPs and how long the engine has been shut down for.

Yes, there are limits on minimum idle time before takeoff and after landing.  It's often 3 minutes. If you go more than the minimum, the LCF life would be extended.  Maybe not by much, but it would be better. The engine is not at thermal steady state after 3 minutes.

My main point was just that taxing out on one engine definitely does not "wear out" that engine.


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Are there any ducted propeller or fans without a shaft in the centre?
Are there any propeller or fan designs that hold the propeller or fan in the duct and do not have a boss or propeller shaft? This could reduce the drag of the  centre. Are there any other advantages?

When I viewed this question earlier, there were a lot of comments and an answer from naysayers, for instance from a Cessna 172 pilot commenting on turbine engine design. Where did they all go?

Comments are ephemeral. You should not ever expect a comment to last. They can be deleted at any moment without notice. Usually, comments get removed (and moved to chat) when they contain a discussion. Comments are for asking clarifying questions or making small suggestions.

Yes comments are ephemeral. Just wish there would be more positive ones though.

Perhaps an aeronautic version of one of the Voith maritime systems? This one appears to be electrically powered.
http://www.voith.com/en/products-services/power-transmission/voith-inline-thruster-voith-inline-propeller-11014.html (watch the "installation" video).
Also, this video explains the concept a bit (for maritime applications)

I suppose if you could arrange a lightweight frictionless magnetic ring bearing (possibly integrating electric drive), and/or peripheral drive linking system, it might be worth it if you needed to have two or three smaller fans beside each other, driven by a single core, rather than a singe large fan, in order to reduce fan/nacelle height. (imagine a B52 nacelle with one side shortened to just a fan cowling) I doubt that this would reduce overall drag, though, but I am intrigued by the concept of the greatest chord of the blades travelling the fastest.

You're thinking of an exoskeletal engine.  They've been studied, and have lots of theoretical advantages, but the major sticking point that's kept them from being used so far is that we don't currently know how to make bearings suitable for supporting the large spinning rotor drum.


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What are maximum G forces humans can survive?
I read that very high g forces could kill a pilot, brain pushing into the skull.
Is there a way of decreasing or surviving these forces and how would it work if you ignore aircraft capabilities.
If not what is the maximum survivable g force with current technology.

Related answer

Very related answer

I read that very high g forces could kill a pilot, brain pushing into
  the skull.

High G-Forces cause blood flow to the brain to be impeded due to blood pooling low in the body under high acceleration. This causes the pilot to black out eventually.

Is there a way of decreasing or surviving these forces and how would
  it work if you ignore aircraft capabilities.

Yes, most if not all modern fighter pilots wear G-Suits. The basic principal of operation is to constrict blood flow to the lower body to prevent pooling in a high G maneuver to increase blood flow to the brain. The g-suit typically buys the pilot about 1G of increased tolerance. The average human tolerance is between 3G and 5G. Aside from possibly some aerobatic planes I dont know of any civilian or commercial aircraft equipped with G-Suits. Generally speaking good heart health can help mitigate the effects in sustained G situations. This why it is so vital that fighter pilots be in top physical shape as fighter planes are capable of very high G maneuvers.
You can decrease the overall G-Force experienced by altering your maneuver (i.e. not undergoing as much acceleration). However in a combat situation some high G maneuvers may be warranted and thus the suits are used. In civilian flying all deliberate maneuvers are well within human limits.

If not what is the maximum survivable g force with current
  technology.

This depends on the exposure time to the G-Force, see this question/answer.

But the is for passing out, what is the max g force or ways of preventing physical injury such as parts of the body inside the body continuing to travel while the outside has stopped? @dave

Its about sustained exposure over time, there is no hard limit. You can take a look at this article for some ranges. If you provide more text to the question like a specific scenario I may be able to provide a better answer.

This article, https://en.wikipedia.org/wiki/John_Stapp, makes interesting and relevant reading...

There is a mismatch between your numbers. “Average human tolerance is 3–5G” and “g-suit typically buys the pilot about 1G” faill to add up to the 9G that fighter pilots sometimes do.

The 3-5G number is for the average human. Most fighter pilots are in far better physical shape than the average person. Heart health, training, and other mitigation techniques can lead to far higher G loads.

@Dave, this should then also be mentioned in the text.

I read that very high g forces could kill a pilot, brain pushing into
the skull.

Not really. Humans who have been killed by very high accelerations (in the order of tens to hundreds of gs for a fraction of a second) tend to look perfectly fine on the outside, but are a mess internally. The most likely cause of death is rupture of the coronary arteries, followed by massive internal bleeding. Think Evelyn McHale (picture below, source):

These brief but very strong decelerations are typical for aviation accidents. Moving over into the survivable range you will again find tens of gs, but they could only be survived with plenty of restraints. Think Dr. John Stapp (picture below, source).

Now you will argue that you look at accelerations in a different direction. That's my point: There is not a single magic number, but a wide range, depending on several factors:

Duration of exposure. Look at Eiband diagrams to get an idea. At 1 second exposure a well-trained sitting human will survive 10g unharmed and will suffer severe injuries above 30g.
Direction of exposure. Again, look at Eiband diagrams. In a prone position the same pilot who could only tolerate 10g while sitting will survive 40g for one second.
Physical condition: Older and infirm people will tolerate maybe a third of what a young and fit person can suffer through.
Technology: Restraints, anti-g suit, anti-g straining maneuver (a physical technique where the aviator pushes air out of the lungs against a closed glottis, while simultaneously contracting the muscles in the calves, thighs, and shoulders).

A combination of all three enables a trained pilot to sustain 9 gs sitting for several seconds. Proof:

"Centrifuge training for qualifying to Gripen at Sweden" (YouTube)
Additional evidence: When the F8F Bearcat was introduced, Grumman told the pilots not to pull more than 7.5 gs, because at that load the wingtips would come off in order to protect the rest of the wing from overloading. Mysteriously, lots of F-8F returned with their wingtips clipped. Those Navy pilots simply wanted to find out if the protection worked.
When you want to go beyond that, switch to a prone position. That effectively quadruples the limit, on the other hand the straining maneuver will lose most of its effectiveness.

Interestingly, and not so practical for flying but has been studied by the European Space Agency, if you are immersed in a fluid bath you can withstand extraordinarily high G forces, upwards of 24 Gs.
Old question on Physics Stack: Does Liquid Immersion protect against G forces?


text:
Can hypersonic aircraft be agile without the G forces harming the pilot?
I read that high G forces associated with hypersonic flight could kill the pilot.
Is there any way of making this survivable yet keeping agility at hyper sonic speeds (irrespective of the plane's capabilities) and how do they work.

Agility means that you can change the speed vector rapidly. The way this is done in aircraft is to point the wing's lift into the desired direction and then to increase lift as much as possible. The lift force over time results in a kinetic energy change which accelerates the aircraft in the new direction and decelerates the old speed away.
Flying faster means that the kinetic energy goes up with the square of the speed increase. What could turn 90° within 4 seconds at Mach 0.7 will take 200 seconds at Mach 5 when the same acceleration is applied. This makes clear that agility does not survive the speed increase.
What if the force is increased? To regain the same 22.5°/s turn rate would require a lift multiple of 50! This means hundreds of gs for a structure which is weakened by friction heating and a massive increase in wave drag. Since wave drag increases with the square of the speed increase, any hypersonic vehicle attempting to pull many gs will not stay hypersonic beyond the next few seconds! Assuming an L/D of 10, the deceleration would be in the order of 250 g if the wing tolerates 50 g of lift load and things are linearily scaled up. But that would be an L/D of 0.2 - in other words, the wing will be close to 90° angle of attack and the craft will break apart.
Even the more reasonable 6 g of subsonic manoeuvring will mean a 36-fold increase im wave drag at Mach 5, bringing L/D down to less than 2.
Conclusion: There is simply no way for hypersonic vehicles to be agile. The pilot is the least of your problems.

Well, 2 G's is 2 G's, regardless of what speed you're flying.  A level (coordinated) turn with 60 degrees of bank is 2 G's, regardless of your airspeed.  What changes is your turn rate and turn radius; at 20 knots, a model plane at 60 degrees bank can probably complete a 360 degree turn in a few seconds and a radius of maybe 10 yards.  At 300 knots and 60 degrees bank, a conventional jet will need a minute or two and a turn radius of probably a couple of miles.  At 2000 knots and 60 degrees bank, an SR-71 might overfly a few states making that same 360!  But it's all 2 G's for each of those aircraft.
Now if you want the SR-71 or some similar highly supersonic aircraft to have the turn rate & turn radius of your 300-knot Lear jet, then you'll get a LOT more G's -- which can induce various other issues with your supersonic beast.  And if you want either of those to keep their speed while turning in the radius of your 20-knot drone... well, let's just say that you're talking about G forces beyond the realm of all human experience to make that happen!
There are all kinds of discussions that can be had about how hypersonic aircraft can be made more maneuverable without doing things that risk losing control, flaming out the engines, creating unacceptable amounts of drag, and so on, but all of those discussions take place in the context that high speed + high turn rate = more G's, and given any 2 of those factors that you choose (i.e. how fast you want to go & how much G-loading you're willing to sustain), the third is determined.
The max G-loading for a human is pretty well about 9 G's, so pick whatever combination of the other two factors you want.  Or go unmanned -- which with today's technology is probably cheaper.

IIRC SR-71 could, up at the typical cruise flight level, pull only 1.5 G. It simply wasn't intended to do much manoeuvring in cruise.


text:
To what extent can I deviate from the endorsement guidance given in AC 61-65?
Specific case:  I have a student who is ready for his ride, but he has not yet scheduled it, and because I'm moving, I will be permanently unavailable to endorse it in a few days.  I want to add a stipulation to his endorsement that says the endorsement is valid only until a certain date, and it's only valid if he has had some number of hours of flight training within the preceding $x$ days.
Neither of these items are mentioned in AC 61-65.
General case:  How much can I legally deviate from the guidance for checkride endorsements given in AC 61-65?

Advisory Circulars by definition, are advisory and not regulatory in nature (Chapter 1, paragraph 3 of FAA Order 1320.46C). Therefore, AC 61-65 provides suggested language that will ensure compliance with the FARs.  You are free to word the endorsements differently, but if the examiner takes issue with your endorsement, the student may not have any recourse but to have the entries redone (by you, or another CFI).
Since you say your student is ready (I am assuming for their Private Pilot check ride), why not go ahead and endorse them right now? FAR 61.109(a)(4) requires the student to receive 3 hours of flight training within the two months prior to the test, this would cause your endorsement to automatically expire if they don't test (or receive additional training) within that window.
Alternatively, I would suggest contacting the local Flight Standards District Office and get guidance from them directly.

The reason I didn't want to endorse him right then was because 61.109(a)(4) only requires 3 hours within two months, and two months is a lot of time for a new private pilot to build up rust.


text:
What's the difference between TWEBs and TIBS?
Everyone I know knows about DUATS and Flight Service weather briefers, but you almost never hear about TWEB and TIBS.  They have something to do with telephones and recorded weather information...are they the same thing?
What's the difference between TWEBs and TIBS?  When is it appropriate to use each?

Can you exclude me from 'everyone'? Until now, I had never heard of DUATS. Is it a FAA-land thingy?

@DeltaLima DUATS is "a free FAA-sponsored service to pilots, dispatchers and others authorized by the FAA".

@DeltaLima - Fixed.  Thanks!

@SteveV. Thanks! :-)

NOAA has a great guide on their website called A Pilot's Guide to Aviation Weather Services which covers these (and more)!  They actually describe it better than I could.
The short version though is that TIBS is a telephone weather service while TWEB is a recorded route briefing that you can listen to while airborne.  Both are used for supplemental information and don't replace an official briefing.

TIBS Telephone Information Briefing Service
TWEB Transcribed Weather Enroute Broadcast
PATWAS Pilot's Automatic Telephone Weather Answering Service

TRANSCRIBED WEATHER BROADCASTs (TWEB) are continuous broadcasts of
  recorded NOTAM and weather information prepared for a 50-nautical mile
  wide zone along a route and for selected terminal areas. TWEBs are
  broadcast over selected NDB and VOR facilities and generally contain a
  weather synopsis, in-flight advisories, route and/or local vicinity
  forecasts. Winds Aloft Forecasts, current weather reports, NOTAMs, and
  special notices. TWEB outlets are listed below by state:

PILOT'S AUTOMATIC TELEPHONE WEATHER ANSWERING SERVICE (PATWAS), and
  the TELEPHONE INFORMATION BRIEFING SERVICE (TIBS), provide continuous
  recordings of weather and aeronautical information. The information
  may include area and/or route briefings, airspace procedures, and
  special announcements. Telephone numbers for PATWAS and TIBS locations
  are found in the Airport/Facility Directory.

TWEBs, PATWAS, and TIBS are for preflight or inflight planning and
  should not be considered a substitute for formal preflight briefings.


text:
In Malaysia, can someone become a LAME through self study rather than training school?
Is it possible for someone to self study (without attending a training school) and individually sit for the exams required in order to become a B1 or B2 LAME in Malaysia?

Unfortunately, it is not possible to become a licensed AME in Malaysia entirely through self-study. It takes between two and seven years to become licensed as an AME in Malaysia, and that includes two years of practical/on-the-job training at a Malaysian aviation facility/company. You could, in theory, study the theoretical material and try to pass the test, but if you don't go through a Part 147 training program it will take much longer to become licensed.


text:
What is the efficiency of the turbine of a modern jet engine?
What is the turbine efficiency of a modern jet engine? Just the turbine efficiency only. What percentage of fuel energy the turbine converts into mechanical energy.

Possible duplicate of Which jet engines have the highest thermal efficiency?

Slide 7 of this presentation (shown above) states the latest technology for a turbine with cooling flow is 89% efficient, while an uncooled turbine is about 90% efficient. The table from this presentation comes from the well renowned book by Jack Mattingly, "Elements of Propulsion: Gas Turbines and Rockets".

89% efficiency surprises me.  Do I understand correctly that this turbine converts 89% of fuel energy into mechanical shaft energy?  I thought that ICE and jet engines are only 35% thermally efficiency.  Someone please clarify this large discrepancy.  thanks

@Nevillep.  To clarify completely is beyond the ability of what one can say in the limited text of a comment. But, the 35% you mention is about correct, and is the overall thermal efficiency of gas turbine. It is how efficient the engine is converting the calorific energy of the fuel to thrust. The 89% efficiency is the (isentropic) efficiency of just the turbine section of the engine. It is a measure of how efficiently the turbine extracts energy from the gas flow, for the given pressure drop across the turbine. The overall efficiency is determined by the efficiency of many individual ...

...parts. For example if there were 4 parts each with 90% efficiency, the overall efficiency is 0.9 x 0.9 x 0.9 x 0.9 = 0.6561.  So, the overall efficiency is low but the efficiency of individual parts is higher.  Your question specifically asked for “just the turbine efficiency only”.


text:
Please identify this twin-engine airliner
Could someone please identify this aircraft for me.

HI, This aircraft is Qantas Airbus A330-300
Manufacturer Serial Number (MSN)----->564
Age 14.9 Years
current registration---->VH-QPC
Test registration------>F-WWYQ
Production Site---->Toulouse (TLS)
Airframe Status--->Active
Enjoy, cheers !!
source:https://www.planespotters.net/airframe/Airbus/A330/VH-QPC-Qantas/ZQNhDG

I can't see any way you could work out from the original image it's this particular A330? Also the photo and data just seems to be copied from here, you should cite your source: https://www.planespotters.net/airframe/Airbus/A330/VH-QPC-Qantas/ZQNhDG

@PeterJ, definitely better to cite the source, but he was right... that's a Qantas' bird ;-) Look at the red under the tail on the fuselage and the reg. number under the left wing.

@PeterJ, the one in the question. :-)

I concede that it is a Qantas jet. But Qantas owns 28 A330's. How did you determine that it was this specific aircraft?

While waiting for al Maghraby to explain, I'm guessing that he drew his conclusion from the registration number under the left wing. Enlarging this reveals that it is VH- + three letters, first is O or Q, second P or B, third C or G. The only matches in Qantas's registrations are QPC and QPG. Don't know why it couldn't be VH-QPG.

@A.I.Breveleri , Sorry for the late response, I do agree with your last comment regarding how I determined the registration. But as you said it could be VH-QPG.

That appears to be an Airbus A330.


text:
What does a dot inside two parenthesis mean on a weather depiction chart?
Earlier today, a friend asked me what this symbol (referring to an airport in Canada) on a weather depiction chart represented.  I didn't know. (Full chart available here)

What does a dot inside parenthesis mean on a weather depiction chart?

@Articuno - The Aviation Weather Center.  I've edited in a link to the full chart.


text:
What is the weight that is used to balance an aircraft called?
I remember I was reading about balancing an airplane a few days ago, and i came across a type of weight that is added to balance the airplane. But, I do not remember what it was called.
Also could someone tell me the approved location of these weights on a Boeing 747-400?

Related: Water Why would a glider have water ballast? and fuel Is passenger weight distribution important on a commercial flight? Also for flight testing and conspiracy theories.

747s in everyday operation typically use fuel for ballast when needed. Ballast fuel is considered to be part of the zero fuel weight and you are not allowed to burn it, although obviously if you were about to run out of fuel, it's available.
Ballast fuel is carried in either the center tank or distributed evenly in the four main wing tanks. Individual carriers have different ideas insofar as their preference for either center tank or wing tank ballast fuel. Also, after the TWA 800 explosion back in the late 1990s, there were as I remember special rules for a time on carrying ballast fuel in the center tank.
Should you wish to explore the effects of ballast fuel on the CG of a 747-400, go to 747.terryliittschwager.com and select the first aircraft N402YY. When the aircraft comes up, you'll notice that the BALLAST FUEL radio buttons at top center have the Center Tank selected. If you put 100000 lbs of fuel in and then 1000 lbs of ballast, you'll see the zero fuel weight CG change from 30.6% MAC to 30.8% MAC.
Ballast fuel is more often necessary for 747s that were originally passenger airplanes and then converted to freighters than otherwise. The problem is that the heavy structure added for the large cargo door aft of the wing brings the basic operating weight CG farther aft then before the cargo conversion. 747s originally manufactured as freighters do not have this problem as they have additional structure for the nose cargo door in addition to the side cargo door structure.

I am pretty sure you are thinking of ballast. These kinds of weights are used aircraft and in many other types of vehicles as well, particularly in ships, to maintain proper balance.

Get it? But seriously thanks.

It is called ballast - part of the inherited ship terminology- or counterweight. Placed where it produces the necessary torque for balance. Usually in the nose or tail. I don't have data specific to 747-400 but here's a somewhat related article.

It is usually called as ballast. From Wikipedia:

Ballast is removable or permanently installed weight in an aircraft used to bring the center of gravity into the allowable range.

Could you tell me where they are placed on a Boeing 747-400?

@DevanshRathi It depends on requirements- for example, for example, in this article, they are placed near the nose. During flight testing, they are shifted around to determine the effects of shifting cg on the aircraft.


text:
When flying VFR without GPS, how do pilots know if they are inside controlled airspace or not?
How do VFR pilots know whether or not they are inside controlled airspace if they don't have GPS onboard?

Sad state of affairs when newer pilots have no idea how to get around the old way.  GPS is starting to cause VFR pilots' navigation skills to atrophy and some day when a solar storm brings the whole satellilte array down, it's gonna be a problem.   Always carry a paper chart, and use it from time to time.

@JohnK - that's a typical grumpy old man argument about old ways fading. This is a non-argument because if a solar storm of that intensity happens, some VFR pilots being a bit lost will be least of our problems.

Or when the government turns it off because of terror attacks or wartime necessity. Which also necessitates moving stuff. Railroads are chewing their fingernails off over that, because mandated Positive Train Control is a lot easier to build if you have GPS -- but you can't shut the railroads down in wartime, now can you?

@Harper Fortunately every other capable nation is launching/has launched their own satellite location system for this very reason.

@John K - You can't just fault GA aircraft for decline of seat of the pants skills. The FAA reports an increase in accidents after glass cockpits,i.e. Air France flight 447 (for 3-1/2min the pilots failed to correct for a stall).

@Brad that will help their military, not you. GPS and Galileo are both NATO, so will move in lockstep. Everyone hates terrorists and will support an antiterror civilian blackout. Conflict parties will blackout. Does your device even support the uninvolved network? Also, anyone will blackout if the Navy says "or else... we find out if an SM-3 can hit a navsat."  Because the debris from one kill will mostly stay in that orbit and eventually take out their whole constellation.

My airplane has a bubble canopy so any GPS works fine and after trying a tablet with Naviator I now just use my phone with with it.  So I'm just as addicted to the tech toys as anybody, but map reading and navigation by pilotage (I'm an ex bush pilot) are deeply ingrained.

@jwzumwait Yes, but part of it is the airlines have been, in the mistaken interest of safety, driving pilots to use their automation as much as they possibly can, letting stick and rudder skills atrophy.  In the case of AF447, I think you had a case of a pilot who didn't REALLY know how to fly in the first place, if you know what I mean, so that when he went into a mental saturation state under that stress the basics left him and he was lost, compounded by a relief pilot in not much better shape mentally.

@John K - I agree, I believe every hour I actually flew a C-150, C-172, or Piper is worth 10hrs B747 time :)

@Harper "or else... we find out if an SM-3 can hit a navsat." Lol. SM-3's can barely hit LEO let alone MEO " SM-3 has also been employed in an anti-satellite capacity against a satellite at the lower end of low Earth orbit." have you ever looked up launch specs and wondered why payload to LEO is 3x that payload to GTO? Do you understand the velocity involved? or the volume? No one with any experience is worried about debris in the GPS orbit.  LEO because of how much stuff there is and GEO because it is 1 dimenstion smaller but not MEO.

@Sam I didn't claim an SM-3 could, nor does the statement's purpose require me to.  Grats on the technical knowledge but in your rush to dazzle us, you seem to have missed the big picture: USA thinks your GPSlike is killing its citizens, and it's flat-out stating its intention to do something about that. Now do you want the USA's undying (literally) gratitude, or what's behind door #2?

I was a CFI about the time GPS started coming out in aviation. One of my best lessons was a fairly routine x-country flight with a student and his new GPS. He spent time setting it up, prepping the course, beginning the flight and starting to navigate off the GPS. About 10 minutes into the flight I reached up and flipped his GPS off. He flipped it back on. I turned it off again, and he asked me why I did that. I told him he just had a GPS failure; now what? After some grumbling, he broke out a sectional and plotter and navigated. Tech is very cool. But fundamentals are cooler when tech breaks.

@Davor I'd like to particularly point out the irony of luddites being worried about us not being able to fly planes in case GPS is shut down :)

@Davor: No, it'll be literally one of the big problems you have to worry about. It seems you overestimate how much it takes to knock out GPS. Over-reliance on GNSS in general is a huge problem worldwide and that's not a "typical grumpy old man argument" in the slightest.

Amazing. People have forgotten that 'maps' were a thing!

These guys managed to spoof GPS without too much difficulty (in a Faraday cage) - unless you have a special military receiver that can use the encrypted military-use-only signal, which you don't.

Back in days of the dinosaurs, there were things called 'maps', made from dead trees. You can still get them. They will still keep working even after the batteries have run down, and a Carrington event has wiped out electrical infrastructure. Unfortunately you need to practice to get the best out of them, for which GPS robs you of the motivation.

@LightnessRacesinOrbit - so when was the last time a GPS outage happened?

@Davor: Systemically? https://www.gps.gov/cgsic/meetings/2016/curry.pdf But the real risk is not the system, it's the weakness of the signal and how utterly trivial it is to spoof/jam locally. £10 on eBay buys you a jammer to put in your car's cigarette lighter socket and kill GPS outwards and upwards for like a mile. You really want to be relying on that technology while you're in a plane?

VFR aviation maps called "sectionals" (and now GPS map displays) depict the types of airspace through borders with different colors and dashed lines. You can buy or download the maps for free from this FAA site.
It is always the responsibility of a pilot to know where they are and follow all applicable laws. In the US, a pilot that breaks a rule because they didn't check NOTAM's can expect certificate action. NOTAM's will inform the pilot of TFR's, "hot" military zones, and other important regional and local (i.e. airport) regulatory information.
I got my PPL in 1975 and still carry maps with me. I plot an "X" along my route every 10min of flight time (20-30mi). As I reach each checkpoint, I follow a very old axiom, "Never.. Ever.. EVER!.. proceed to the next checkpoint until you identify where you are and what corrections are needed for the next checkpoint". In this manner, you can never be further than 1 or 2min and 1-2 mi from where you should be.
Even when sightseeing with no particular route, I routinely mark a map about every 10min with my location. In my 2500hrs of flying, the most I have ever been off  in my navigation was 10mi (even when flying 1500mi x-country). So, knowing where you are is not difficult if you practice the skill.
The front of the map has a legend to remind pilots what the coloring stands for.

Sectional map (US Gov public domain)

Front map legend (US Gov public domain)

I got my ppl about 15 years ago but haven't been able to fly much because of school. I hope sectionals are still something they teach about when you learn! I'm shocked this is what the OP is taking about!

It might be useful to note, that the symbols are not completely unified between different countries, so when flying internationally, mind to check the correct legend.

@JanHudec not just symbols, but airspace names and procedures. Never assume that just because it works one way in the US it works that way everywhere. I'm currently working on my EASA PPL, 20 years of PC flight simulators helps a lot but procedures and stuff are quite different from how the sims portray them as they're built around US FAA procedures, not EASA procedures.

"Charts", not "maps".

The one major thing missing from this answer is how you identify where you are (in relation to your checkpoint). Ground references, VOR/DME, intersection of VORs, etc. Plotting where you are on the chart is impossible if you don't know where you are, which is really what the question is asking...

In the UK, you are still legally required to carry a paper chart. We also still learn navigation without a GPS map, and fly our qualifying cross-country without any GPS on board. It's nowhere near a forgotten skill.

Use of a sectional chart and pilotage.
You will have to be aware of where you are using ground references while cross referencing where the boundaries of controlled airspace lies in relation to those references.
For example if you’re flying around to the west of John Tune (KJWN) airport in Nashville, TN and will notice the river bends near the airport.  Anything to the east of them lies in the Nashville Class C shelf between 2400 and 4600 ft MSL.  A similar process can be used to assess your position relative to the surface area of the Class C airspace.

You can also pinpoint your location if your aircraft has two NAV radios and OBS heads using the intersection of two VOR radials or one NAV radio and a DME by locating you polar position relative to the VOR.

Generally: By Using a (Physical) Map
Aviation charts have landmarks and airspaces on them, which you can use to estimate where you're at. Other answers give great examples of this already, I don't have to repeat it.
But I thought I could add some real life experience here:
1) Memorizing the Area
Glider pilots, especially trainees, often fly without maps and GPS. As they tend to stay close to their departure airfield, they can be sure to not get into controlled airspace. Trainees generally memorize beforehand where such airspace begins, for example at my old aviation club we knew we had to contact a nearby airfield when going above a certain altitude, and going past the nearby city to the north would also lead into that airspace.
This of course restricts these pilots to only flying within this well-known area, as anything beyond could or could not be controlled.
2) Planning a Route Ahead of Time
I have flown cross country without any GPS for training purposes when I was a student pilot. My trainer and I plotted our route using the map before even going to the airport. We planned to fly along highways and other highly visible landmarks in order to keep our orientation and avoid controlled airspace. This way we barely ever needed the map while flying and still knew where to go.

An iPad map would suffice.  They're not Net connected in flight, are they?

@Harper, a paper map has a very, very important advantage—it can't run out of power!

Or overheat in a hot cockpit...

@SteveV. clearly you've never had a map spontaneously combust in front of you. It's quite frightening! (I jest)

@Harper depending on the navigation app, some are some aren't. Those that are would require an iPad with 4G or a linked iPhone with a working hotspot.

@Harper you can of course use a digital map, too. But when using an iPad or similar device you might as well turn on it's GPS ;) Positioning works even without an actual network connection.

@immibis I've singed a map while reading it with a magnifying glass. Not a pilot, was out camping/hiking.... fortunately noticed the smell, map only had a brown spot on it.


text:
If a pilot ejects, what is the autopilot programmed to do?
If a pilot uses their ejector seat during flight, what is the autopilot programmed to do?
As a developer myself, I'd want to build in a way for the plane to try and save itself if possible (to save money) by auto-landing, or at the very least, calculate the nearest least-populated area for a crash-landing. So I'm wondering if anything like this is even written into the software.

Not many situations where the pilot needs to eject, and the autopilot is active -- usually you'd have that off if: being shot at, doing high-energy maneuvers, landing or taking off, etc.  And once you need to eject, activating a near-useless autopilot is likely to be the last thing on your mind.

I wonder if the auto pilot even knows about the ejection.

@ymb1 I can't imagine how bad the ribbing Captain Faust got after that must have been.

@ceejayoz Ribbing in person would have been a lot better than at his funeral, so I'd say whatever he got was worth it.

I suspect the military preferred option for some aircraft (e.g. classified stealth aircraft) would be to cause the most self-destructive landing possible - the last thing they want is for the aircraft to be recovered by the enemy.

@ZeissIkon And once you need to eject, activating a near-useless autopilot is likely to be the last thing on your mind. Ofcourse, the AutoPilot could activate on/by the pilot's eject button/switch/handle. If it would do any good is another matter.

Generally, ejection seats are used in a situation where an autopilot isn't going to do much good, i.e. loss of control, parts of airplane missing, aircraft in an unrecoverable spin, etc. No pilot wants to bail out, and it when they do it's because a very bad choice is the best option available.

@ceejayoz: Apparently, the ribbing started while he was still parachuting down.  "Gary, you'd better get back in it!"

@abligh, military aircraft (at least Russian ones) generally have small explosives that destroy the most classified systems on the airplane (such as IFF). I don't remember with certainty, but they should activate in case of ejection. In any case, the pilot is required to activate them if the airplane has a chance to end up in the enemy hands.

You're assuming that the airplane HAS an autopilot - many fighters don't have, since they have a highly-skilled and trained manual pilot.

Upon ejection, I would have the plane do its best to lawn-dart. No need to leave anything to the scavengers.

@RAC Uh, yeah, military fighters definitely have autopilot systems.  Missions aren't dogfights from takeoff to landing, and pilots need time during missions to check maps, adjust instruments, and whatever other cockpit management.  There is some flying just to get somewhere and AP allows multitasking in those scenarios.  There are also ferry flights where you wouldn't want to be manually holding straight and level for hours without a break.

I'm wondering if anything like this is even written into the software  You can keep wondering, as nobody spending Ministry of Defense, or Department of Defense, money on aircraft subsystems will waste their money on such a pointless piece of software.

Most fighter type aircraft (A-10, F-16, F-15, T-38, T-6) do not have an autopilot.

I would want to build in a way for the plane to try and save itself if possible (to save money) by auto-landing

Had the situation allowed saving the airplane the human pilot would definitely have tried that first. The fact that a trained fighter jet pilot decided to eject from an aircraft knowing that the ejection was a last resort and could be deadly, signifies that the plane was not able to be flown safely anymore.
On top of numerous irrecoverable problems at that point, one of the most significant issues is the fact that ejection destabilizes the flight path and the increased drag (because there is no longer a canopy on top) makes it even harder to safely glide that jet, let alone land it somewhere.
There is nothing much autopilot can do at that point.
There have been two famous incidents that are related to your question but afaik neither of them involve Auto Pilot.

1989 Belgian MiG-23 crash
Cornfield Bomber

It's just like saying I know the airplane can be saved but my computer will take care of it, I'm outta here. See you at the Court Martial.
Some commentators have noted that I did not answer one basic question:

Don't forget to answer the question "If a pilot ejects, what is the autopilot programmed to do?", even if the question seems moot

This question is too broad: there are numerous models of fighter jets all around the world, built by a number of manufactures and internal details of which are closely guarded secrets. You are not going to generally find out a manual on the web listing all the actions that the autopilot software will perform after a bail out. If the OP can narrow down the question to a certain model one can research and try to find something but I don't believe its going to be an easy find. Hence I'm sorry I don't have an answer to that question. I hope someone more knowledgeable goes ahead and posts an answer to that.

Yeah, thank you for letting me eject on my side of the border, here take our airplane and all its secrets on your nearest runway

Or in peacetime, the plane wreaks havoc by going to the nearest airport and landing, ignoring air traffic control, deciding for itself which runway is active, and disregarding whatever is happening in that airspace and on the ground.

@rclocher3 With those autopilot capabilities, one begins to wonder why a human pilot would be necessary in the first place!

At least in the first case (Mig 1989 crash) autopilot was involved. From Wikipedia: "At an altitude of 150 meters and descending, the pilot assumed he had a complete engine failure and ejected without incident. The engine had not failed completely, and the aircraft remained airborne, flying on autopilot in a westerly direction"

Yes that is true but note that it was a very crude form of autopilot. In R/C aviation we call it a fail safe in hold mode. So all that the system did in that case was to hold the last commands that were given to it. It did not make any adjustments to avoid something.

Don't forget to answer the question "If a pilot ejects, what is the autopilot programmed to do?", even if the question seems moot.

You've explained why you think autopilot would be useless, but haven't actually answered the question: "what is the autopilot programmed to do?". The answer may be "nothing", because of reasons stated in your answer, but there may be more to it. You should at least try to answer the question.

When a car crashes, from my understanding, the ECU will typically turn off the fuel pump such that (additional) fuel is not pumped into any possible fire by the fuel system. Wouldn't it make sense for an aircraft to do the same? At the very least, the flight computer (not the autopilot) could shut down the engine(s), turn off the fuel pump(s) and shut off power. Furthermore, are there really no realistic cases where the autopilot could attempt to crash land the plane? Even I have seen multiple videos where pilots have ejected because of a lack of a safe place to land, e.g. on bird strikes.

@AlphaCentauri It's definitely feasible to develop. The algorithm for a completely autonomous transition from arbitrary point in the air to parked on the tarmac just isn't part of current autopilots, even though most of the basic building blocks (nav, autoland) required to put it together are.

Good answer. I'd also add that a USAF DC-3 in 1957 landed itself perfectly when it ran out of fuel and the crew bailed out http://www.dc3history.org/dc3fliesitself.html.  The DC-3 certainly did not have autopilot

"I know the airplane can be saved but my computer will take care of it, I'm outta here. See you at the Court Martial." I was laughing out loud for several minutes over this. Amazing. xD

Another related incident is https://en.wikipedia.org/wiki/2002_Jalandhar_MiG-21_crash (don’t think auto pilot was involved in this one either).

I can imagine a situation where a pilot would eject because the pilot could not save the jet themselves. For instance if it requires a sharp turn that would induce too many G's of force that the pilot would pass out before the manouvre is completed. It then would be nice for the plane to be able to safely land. especially in training conditions.

If the pilot has passed out how will he or she eject?

I wonder if it would be worth considering maneuvers (especially with vector engines etc.) that would recover the airplane but kill the pilot to be done after the pilot ejected, but then how to test that...

To add some context to the other answers...
Ejection is not a safe thing to do.
The two most popular ejection systems today, the ACES II and Martin-Baker, have around a 90-92% success rate... the definition of success being the person lived. Most ejections result in some injury to the person, as it is a fairly violent activity, with a brief 20g impact when the seat fires.
Almost all ejection occupants will suffer some form of spinal compression, typically they'll lose half an inch of height. If the person doesn't follow protocol exactly, they may lose an arm on the way out. If the head isn't perfectly in line with the spine, the neck can be broken.
Ejection is a measure of last resort, to be used only if the only other option is certain death.
So it's pretty much a given if the crew member fires the ejection seat, there is no other viable option, and the aircraft is uncontrollable, or will very soon be uncontrollable, by a pilot or an autopilot.
Also, if the aircraft is gyrating wildly, the seat can malfunction, or the occupant can be struck by parts of the aircraft, so waiting until the aircraft is completely out of control isn't a wise move, either.

That’s a great answer.

Question: Is there a second, less-violent mode for ejection seats if you have perfect conditions? For example the aircraft is fully functional, but you will ran out of fuel and there is only wood/water, so you really cannot land safely, if at all.

@ThorstenS.: No, the ejection system is strictly binary: fully in/fully out. Anything else is a malfunction (you don't want to eject halfway, or sort-of-eject and immediately get hit by the rudder). The thing is complex enough without a trim knob ;)

Self destruction sounds like an excellent idea for military planes in contested space (provided it doesn't kill the ejected pilot in the process)

@Nelson I read a great article about the B2 bomber. The journalist was able to fly but was not cleared by medical. In fact, at his over 6' height, if an ejection was required during the flight it would have removed his legs. So, there's that.

@WayneWerner: Ouch!  How so?

@Sean at 6'5" apparently his legs and feet might strike the console, which would be unfortunate. Here's the article (still a good read the 2nd time around)

Whatever it was programmed to do at the moment the pilot ejected.
Ejection seats are complex enough without integrating special processing of the event into the autopilot. Since the autopilot can't land even an intact plane on its own, there's nothing it could do to save the plane.
Some ejections are indeed performed from aircraft that could potentially be saved, and have been landed with similar damage. It's a matter of avoiding excessive risks from a gamble for an 80% chance of a safe landing and 20% a violent crash that sets the deck park on fire. For certain historical reasons, many navies maintain an understandable bias against fires on the deck, and would prefer just ditching one plane. On dry land, there's more latitude for crash landings.
As for preventing (or causing) collateral damage on the ground, the only way is for the pilot to point their plane somewhere and pray. The autopilot is a reactive system - it doesn't concern itself with what's wrong or model the aircraft, just corrects what happens, so, possibly counterintuitively, it's often not too bad at controlling a damaged plane.
Since fighter control surfaces are large enough to counteract a lot of damage-induced drag, a working autopilot has a chance to maintain its last heading even with a damaged craft. And that's as good as you could get with the current level of flight automation.

In particular, when ejecting from large aircraft (eg. bombers) or when the aircraft is currently flyable but shortly won't be (eg. uncontrolled engine fire), it's common to set the autopilot to hold "straight and level" to make ejection easier.  If they've got time, the pilot might additionally aim the plane for the nearest large body of water or other unoccupied area.

@Mark Yeah, fly away from civilization and towards water would be a good last order.  Also, in wartime you might like something that causes it to auger in once it's down to a few thousand feet.  There's also the plane that can be flown but can't be landed--anything that takes the minimum airspeed high enough that there isn't a runway long enough.

@LorenPechtel: Well when you can land with one wing: https://theaviationist.com/2014/09/15/f-15-lands-with-one-wing/

@Joshua Sure, but it needed a lot of runway due to the high landing speed. Had it been a bomber instead, there would probably be nowhere (outside of Edwards) with a long enough runway.

@Skyler great and now I'm imagining a situation that involves refueling a 1-winged bomber long enough to make it to Edwards.

@Joshua But note that he had to land very fast.  That plane was capable of landing on the available runway despite that speed.  More damage or a heavier airplane could take it beyond any available runway, or beyond what the wheels could take.

+1 If you build into the autopilot the ability to do something special on ejection, you have to program in a whole lot of safety checks that it won't falsely detect an ejection. Much better to have it ignore the possibility, since it won't be able to do anything anyway.

It generally does nothing. When a pilot ejects from the plane, that bird is screwed beyond saving. There is no autopilot in the world which is sophisticated enough to fly a military plane even when it's fully intact, let alone when it's on fire and going down.
However, as I heard, there was a Su-27 model (or some descendant of the Flanker, maybe just a prototype?) which had a peculiar easter egg: after ejection the onboard voice announcement system (the female voice which warns the pilot to certain things) talked for the last time: "Good bye, and thank you on behalf of the fleet." There was nobody to hear it, and the pilot's helmet has already been disconnected by this time, so it was really just some engineer's idea of a joke. I don't know if it's an actual feature in current Russian naval Flankers.

Welcome to aviation.SE! Do you have some sources that you can link to? The comment that "there is no autopilot in the world which is sophisticated enough to fly a military plane" is confusing because we know that at least some military aircraft do have them.

Haha that is amazing, I wonder if it ever said that in practice

Perhaps they didn't have much faith in their ejector seat.  Maybe it also dispenses a large glass of Vodka for the hapless occupant.

Soviet/Russian seats were always very reliable, even back in the Cold War. It was really just some engineer humor at work.

Sources are scarce on this. I heard it from a Hungarian fighter pilot who in turn heard it from a Russian. As for autopilots, sure, there are experiments, but there is no system which can reliably pilot a fighter plane, particularly not a carrier-based one. It's still science fiction.

This is backwards.  A modern fly-by-wire control system is basically an always-on autopilot that gives consideration to the pilot's input.  Giving it basic hold modes in addition to maneuvering ones is comparatively trivial.

@TamásPolgár Where have you found information that carriers do not have an autopilot?

Hmmmm... If an airplane talks to the pilot after he has ejected, does it make a sound? But seriously - there's way too much "I heard this from a guy in a bar who got it from someone who oughta know". Tell you what - take up an Su-27, climb out of the seat (but still in the cockpit, but out of the way of the ejection seat), trigger the seat, stay plugged into the headset, and you tell me what happens next, OK?

These things are called anecdotes. Anyone looking for solid evidence to everything, go to a technical library.

@BobJarvis Hi Bob, just did this. Can confirm story is true.

@BobJarvis PS, how do I land this thing now?!

@Cloud: no worries. The aircraft has an autopilot and will land itself shortly (for sufficiently small values of "land" and sufficiently large values of "crater". :-)

I imagine there's probably a switch such that over enemy or unknown territory the plane self-destructs. But you don't want this over your own training areas such that some kind of controlled landing may be programmed in when in training mode.

Military aircraft "self-destruct" is actually kind of boring. It's more of a frying of circuits than a dramatic explosion.

This answer seem wrong. Do you have any references to support it?

You're right - you "imagine". There is no "make the airplane explode" switch.

@DmitryGrigoryev I apologize for not having sources, but these planes are full of technology.  Countries go through great lengths to destroy downed planes so that nobody can reverse engineer them.  In fact, these events are kept as secret as possible, making finding sources difficult.

authors: Bob Jarvis - Слава Україні


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Why are the windshield wipers in the A320 power-up checklist?
I was watching the startup sequence for an A320 and it struck me as unnecessary minutiae to ensure the wipers are off before power on. Is there something important that I'm missing that puts windshield wipers in the same list as thrust and gear levers?

Cant depart the gate if you cant see where you are going - not as relevant on a sunny day, but its in the checklist for that reason.

@Moo makes sense, but the power-on checklist is to ensure the wipers are in the off position before starting the APU. I clarified the Q a bit.

Related: Aircraft ice and rain protection. They must be off, in their park position, to prevent damages due to a dry windshield. Repellent on a dry windshield is also a problem. On the other hand I believe they must be operational for landing on Cat II or III.

Wouldn't it also make sense to check that they are operational?

@SimonRichter it would... Asking about that would make a great new question.

For the same reason you should turn your wipers off when you shut off your car (since very few people go through a power-up checklist in their car...):
Running the wipers on a dry windshield can damage both the wiper and the windshield as the dry blades drag small particles of dirt, grit, rocks, etc across the windshield. These particles can tear up the rubber of the wiper, and they can scratch the windshield. Dragging dirt and rock particles across a wet windshield isn't inherently good for either wiper or screen, but the water acts as a lubricant and significantly reduces the damage potential.
It's far cheaper to print an extra line in the check list and have the pilots take 5 seconds to check it than it is to replace wiper blades and windscreens.

Sounds a little like the reasoning behind me always giving the gear stick a sideways nudge before releasing the clutch in my manual transmission car when the car is standing still: It takes next to no time and greatly reduces the risk of costly damage to the equipment (the car's transmission, in that case). Finagle's Law applies: the one time you don't do it, you can rest assured that it will be the one time it's in the wrong position, and you get that "oh, crap" wakeup call.

Great answer, thank you. Definitely makes a lot of sense, especially considering what an FAA certificated wiper blade and windshield must cost!

+1 on driving a stick, @MichaelKjörling! I do too, and it took a lot of hunting to find a decent one! We now return to our regularly schedule airline programming

@user I've driven a car with a manual transmission for years and I've never heard of that one.  What is the point of nudging the stick?

@rclocher3 the point is to move the stick side-to-side to ensure it's in neutral instead of in gear before releasing the clutch. Of course, if the engine's off, it doesn't matter, but if it's running, letting the clutch out when in gear leads to the car lurtching and/or killing the engine.

Thanks @FreeMan, that makes sense.  I thought he or she was talking about getting the car rolling after being stopped.  BTW I don't wiggle the stick before taking my foot off the clutch when I think I'm in neutral, and I have lurched the car a few times over the years, so perhaps I should adopt that helpful habit.


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In the context of aerodynamics, what is a polar?
Many aerodynamics discussions (including several on this site) talk about "polars" without ever explaining what they actually are.
As with any technical term common to a field, once the community has become accustomed to using it, it's easy to forget that not everyone knows what it means and that a person who never learned the term is unable to follow the discussion. This question hopes to prevent that.
In aerodynamics, what is a polar?

Near-duplicate, but answers the question of why rather than the definition of what

Does this answer your question? Why are the power and drag curves called polars? That's a duplicate, since reading it will also tell you what a "polar" is

@DJClayworth - If you already know what a polar is, that question will certainly confirm it, but that's not the point of this question, which is intended to be found by someone who doesn't know and is searching for 'what is a polar'

IMHO, questions like this are fine and there is no need to close them as duplicate. However, this would be a great example for a self-answer, since you already know the answer.

Could even be made a community wiki answer if you're not looking for the rep...

A polar is a variable that is tabularized or calculated with respect to an angular value. Examples in aerodynamics include coefficients of lift or drag with respect to angle of attack.  The data may be presented in tabular format, on polar axes or on Cartesian axes.
As sophit pointed out, and as is explained in this question Why are the power and drag curves called polars? The name "polar" has been historically applied to the very useful plot which compares the lift and drag information to one another, bypassing the angle of attack information.  The etymology of the naming has an obvious explanation, which may be an interesting research project that could be linked by the interested reader to the linked question above.

The original diagrams of Otto Lilienthal did not bypass angle of attack information but added the angles of attack to points along the curve. When used to reading those diagrams, one can extract more information from them than from a Cartesian plot.

Whenever a body moves in a fluid, its interaction with the fluid generates a force on the body. This force is decomposed in a component perpendicular to the direction of movement plus a component parallel to it. The first component is called lift and the second one is called drag. The lift can be positive or negative while the drag is always positive in the sense that it always act against the movement of the body i.e. it always tends to slow down the body. Both these components depends (among other things) on the relative orientation $\alpha$ of the body with the flow. $\alpha$ is called angle of attack. If the body has as shape (like an airfoil or even an A380) such that it generates 1)lift in a controlled way and 2)drag in an amount as small as possible, lift and drag have a quite typical trend versus $\alpha$:

Lift and drag of NACA 0012 airfoil, from NACA-TR-460. Source: https://ntrs.nasa.gov/citations/19930091108
In this picture I highlighted the drag in red and the lift in blue. As said, drag is always positive and lift can be both negative and positive. The lift has a typical linear trend with $\alpha$ while drag has a typical u shape. An important thing to observe here is that for each $\alpha$ there is only one value of lift and only one value of drag. That implies that we can get rid of $\alpha$ and plot lift versus drag: this plot is exactly the polar (highlighted in yellow in the following picture):

Polar of NACA 0012, from Improving Airfoil Drag Prediction by Ramanujam, Özdemir and Hoeijmakers. Source: https://www.researchgate.net/publication/304104830_Improving_Airfoil_Drag_Prediction/download
The answer to this question:
What are these points in this drag curve ("Lilienthal'sches Polardiagramm")?
gives a nice explanation of the meaning of some points laying on the polar, highlighting the usefulness of the polar diagrams.


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Why did this Cirrus deploy the parachute while ditching over Pacific Ocean?
In this incident near Hawaii, a Cirrus SR22 had fuel problems and deployed its airframe parachute.
My question is why did the pilot deploy the parachute rather than perform a "normal" ditching procedure in the ocean?
For reference, here's the video.

Much better chance of a successful outcome.

Just to add context to the below answers: A Cirrus SR22 has fixed landing gear. This makes a conventional "ditching" onto water VERY perilous.

But why did he run out of fuel is also another question

I read somewhere that he had a problem with a fuel tank.  But I haven't been able to confirm that.

First, according to one operating handbook for the Cirrus SR-22 (there are several versions out there), pulling the chute is the correct ditching procedure (CAPS is the parachute system):

Ditching

Radio ............................................ Transmit (121.5 MHz) MAYDAY giving location and intentions
Transponder...........................................................
  SQUAWK 7700
CAPS .............................................................................
  ACTIVATE
Airplane.........................................................................EVACUATE
Flotation Devices ............INFLATE WHEN CLEAR OF AIRPLANE

Second, the conditions were reported to be windy with high waves:

Weather conditions at the time of the rescue were seas of 9 to 12 feet
  and winds of 25 to 28 mph.

Those would be tough conditions for ditching in. I've read several times that when light aircraft ditch, the pilot and passengers usually survive the impact but they often struggle to exit the aircraft successfully. This article and video explain in detail how difficult it can be to exit an aircraft in the water, even in good conditions. If the aircraft flips or cartwheels then exiting would be extremely tough and the rough sea would make it much worse. Since the parachute lowers the aircraft straight down in a more or less level attitude, the chance of flipping over is greatly reduced. The downside is that you no longer have control of where you touch down relative to the waves, so you might land just in front of one but that still seems like a good option compared to the risk of flipping the aircraft on impact.

In the video, even after the plane was put down more or less flat on the water, it filled quickly with water and inverted in less than 30 seconds.

Great answer.  Thanks for including the info from the PIM, and specifying what CAPS is.

Your link to the video appears to be, sadly, dead.

Once your engine fails the airplane is the property of the insurance company, your only goal at that point should be to survive. Using a whole-airframe chute increases your chances of survival whether over land or sea.
The things that kill people in forced landings of any kind are high-g deceleration and post crash fire. A parachute decreases the chances of both as you have very low lateral speed and much less chance of fuel tank leaks. A parachute also will increase the chance the airplane will remain upright, so escaping the aircraft will be much easier - very important in a water landing!
The only reason for a "normal" ditching procedure is that you have no other choice, using a parachute if you have one will almost always be the right option. The only time I would consider otherwise is if I had enough altitude to glide to a safer emergency landing spot. If pulling the chute would mean landing in water or dangerous terrain but gliding would mean reaching land where a forced landing was reasonable I'd probably opt for gliding.

+1 for the insurance company angle. If you're no longer responsible for the airframe, then why risk life and limb for it.

Pilots kill themselves and sometimes other trying to prevent damage to their aircraft in emergencies. Aircraft can be replaced, lives cannot.

Maybe pulling the chute is the normal ditching procedure for a cirrus with an airframe chute. The splash down looks to be very gentle compared to a normal gliding ditch with fixed gear. It's also less prone to pilot error; once you are dangling there is not much the pilot can mess up.
I imagine the checklist being something like:

pull chute
when aircraft stabilizes open door put on life vest and prepare raft
should plane roll and sink get out and on the raft

Agreed. I would assume that landing on the ocean with a chute would be much gentler than attempting to ditch in the open ocean. Landing on a river is one thing; 'landing' on the Pacific is another.

The odds of survival with the chute are currently at 100% (Per Cirrus) and the odds of surviving a ditching are much less. The plane was lost in the Pacific either way.  The correct thing to do is pull the lever and ride it down, live to be a great pilot another day.  The real question is what did the pilot do wrong to end up in that situation?

I'm not sure about the 100% number. This page lists quite a number of fatalities involved in CAPS pulls.   Maybe you're referring to water-ditching only?

@abelenky or he's referring to the number of deployments in the proper altitude and speed.

"The real question is what did the pilot do wrong to end up in that situation?"  Early reports say that he had plenty of fuel, but due to a faulty/stuck valve on a ferry tank, the fuel couldn't be fed to the engine.   If anything, it may suggest a lack of pre-flight inspection & testing of the newly installed ferry-tanks prior to such a long trip with no alternates.

@abelenky - I'm betting that it was an in-flight failure after 10+ hours of flying/vibration - it seems unlikely that the temporary fuel tanks and fuel system wouldn't have been inspected closely in pre-flight prep. Though maybe having a single valve able to act as a single point of failure was a mistake.

The proper response to losing the engine would be to follow the emergency procedures checklist. In that you will find it says to deploy the ballistic parachute.
While a better option, the ballistic parachute has its own drawbacks. I recall when getting checked out in a Cirrus years ago by an approved training provider that I was told the impact with chute deployed can be up to 8 G's.
So I would say not 100% survivable. Actually I know of a Cirrus that went down near Sanford Florida a few years back that deployed the chute and the occupants died.

According to this page, in that crash (I'm assuming you're referring to the February 2009 Deltona, Florida crash - CAPS event #18), the parachute was fired "immediately prior to ground impact", and the fatalities resulted not from the parachute being deployed, but, rather, from it being deployed too late.


text:
What is the status of "Notes" in ICAO Annexes?
As per the forward to ICAO Annex 11, the status of a "NOTE" in any annex is - "Notes included in the text, where appropriate, to give factual information or references bearing on the Standards or Recommended Practices in question, but not constituting part of the Standards or Recommended Practices."
So, does it mean, a note given in the Annex does not hold any authority as it is not a part of the SARPs ?